Method and apparatus for slitting sheet material

ABSTRACT

A method and apparatus for slitting flexible sheet material of indeterminate length wherein the material is advanced along a predetermined path of travel to and past a slitting station, is formed into a transversely curved configuration as it is advanced, and is slit at the slitting station in a predetermined pattern of spaced, transversely extending rows of spaced slits with the slits in adjacent rows being in predetermined staggered relation. The apparatus includes a circular rotary knife and means for traversing the knife transversely of the curved sheet material. The periphery of the knife blade includes a plurality of spaced cutting edges adapted to penetrate the sheet material to form transverse rows of slits as the material is advanced through the apparatus.

United States Patent Doll 1 Nov. 21, 1972 54] METHOD AND APPARATUS FOR3,456,855 7/1969 Mutter ..83/470 X SLITTING SHEET MATERIAL 3,530,9159/1970 Moriuchi ..83/490 X Inventor: Brendan L. Doll, Patterson, N.C.

Cellu Products Company, Patterson, N.C.

Filed: Dec. 1, 1970 Appl. No.: 94,118

Assignee:

References Cited UNITED STATES PATENTS 8/1964 Naser ..83/678 X 3/1953Allen ..83/176 X 10/1955 Almgl'en ..83/l76 11/1967 Philippi ..83/l76Primary Exa minerFrank T. Yost Attorney-Parrott, Bell, Seltzer, Park &Gibson [5 7] ABSTRACT A method and apparatus for slitting flexible sheetmaterial of indeterminate length wherein the material is advanced alonga predetermined path of travel to' and past a slitting station, isformed into a transversely curved configuration as it is advanced, andis slit at the slitting station in a predetermined pattern of spaced,transversely extending rows of spaced slits with the slits in adjacentrows being in predetermined staggered relation. The apparatus includes acircular rotary knife and means for traversing the knife transversely ofthe curved sheet material. The periphery of the knife blade includes aplurality of spaced cutting edges adapted to penetrate the sheetmaterial to form transverse rows of slits as the material is advancedthrough the apparatus.

16 Claims, 9 Drawing Figures PATENTED I972 3.703,1 l6

sum 1 OF 4 INVENTOR:

BRENBAN L. 'bOLL ATTk RNEYS PATENTEMuvm I972 3.7031 16 SHEET 2 0FINVENTOR: BRENBAN L. boLL ATTORNEYS PATENTEDnuvzn m2 SHEET UF 4INVENTOR: BRENDAN LboL ATTORNEYS METHOD AND APPARATUS FOR SLITTING SHEETMATERIAL The present invention relates to an apparatus and method forprocessing an indeterminate length of sheet material to form a webcapable of being expanded into a relatively open, mesh or net-likestructure.

The broad concept of slitting and expanding flexible sheet material,such as paper, metal foil and the like, has been known for aconsiderable period of time, and is described for example in the presentapplicants prior U. S. Pat. No. 2,656,291. As illustrated in thispatent, the material is formed with longitudinally spaced, parallel,transverse rows of spaced slits, and with the slits of one row beingstaggered or off-set with respect to the slits of an adjacent row. Thematerial may then be drawn or expanded in a direction perpendicular tothe rows of slits to obtain the desired open, net-like structure.

The full commercial potential of the above material has not beenrealized however, since presently employed production techniques arerelatively slow and expensive. In particular, it is known to form theslits in the material by passing a longitudinal length of the materialthrough reciprocating, opposed knife blades positioned transversely ofthe advancing material. The cutting edges of the knife blades areinterrupted to form a row of spaced slits upon each stroke, and the twoblades are operated such that slits of adjacent rows are off-set.

It is believed apparent that the above process is entirely too slow andhas limited capabilities for modern production requirements. Inparticular, the reciprocating knife blades are relatively heavy, and themaximum speed at which they can be reciprocated is therefore limited.Also, the reciprocating blades produce considerable vibration, andrequire a massive supporting structure. Further, any changes in thepattern of the slits is quite difficult and time consuming.

It is accordingly an object of the present invention to provide a methodand apparatus for forming an expandable web of sheet material at greatlyincreased production speeds, and which is capable of producing a widevariety of patterns of slits in a wide variety of materials.

It is a further object of the present invention to provide a method andapparatus for forming an expandable sheet material which obviate theaforementioned difficulties heretofore encountered.

It is another object of this invention to utilize a circular cuttingblade which acts upon the sheet material while it is maintained in atransversely curved configuration.

These and other objects and advantages of the present invention areachieved in the embodiment illustrated herein by the provision of meansfor continuously advancing the sheet material along apath of travel, andmeans for forming the advancing material into a transversely curvedconfiguration. A circular knife blade having an interrupted cutting edgeis disposed within the curved sheet material and is driven to traversethe cutting edge across the sheet material as the material is advancedto thereby form transverse rows of spaced slits.

Some of the objects and advantages of the invention having beenstated,-others will appear as the description proceeds, when taken inconnection with the accompanying drawings, in which FIG. 1 is afragmentary perspective view illustrating the apparatus of the presentinvention;

FIG. 2 is a front elevational view of the apparatus shown in FIG. 1;

FIG. 3 is a sectional view taken substantially along the line 3-3 ofFIG. 2;

FIG. 4 is a fragmentary sectional view taken substantially along theline 4-4 of FIG. 3;

FIG. 5 is a fragmentary sectional view taken substantially along theline 5-5 of FIG. 3;

FIG. 6 is a fragmentary sectional view taken substantially along theline 6-6 of FIG. 3;

FIG. 7 is a fragmentarysectional view taken substantially along the line7-7 of FIG. 6;

FIG. 8 is a fragmentary sectional view taken substantially along theline 8-8 of FIG. 6; and

FIG. 9 is a fragmentarysectional view taken substantially along the line9-9 of FIG. 4.

Referring more specifically to the drawings, the apparatus of thepresent invention is illustrated generally at 10 and includes a framecomprising a generally square rear frame member 12 and an alignedgenerally square forward frame member 14. A number of longitudinallyextending interconnecting members 15, 16, 17, l8, 19, 20, and 21 (FIG.5) maintain the assembly of the rear and forward frame members.

The material to be formed by the present invention is illustratedgenerally at 25 in FIG. 1 and comprises an indeterminate length offlexible sheet material, such as paper, plastic, metal foil and thelike. As the material is advanced from a suitable supply (not shown) toa slitting station, it is formed into a transversely curvedconfiguration for further processing by forming means illustrated inFIG. 5. As there shown, the forming means includes circularly arrangedrollers 26, 27, 28, 29, 30, 31 and 32 which are suitably mountedadjacent the rear end of the machine, and are each disposed to freelyrotate relative to the surface of the advancing sheet material.

At the slitting station, anvil means 34 for supporting the sheetmaterial during slitting is provided and preferably comprises a rightcylindrical supporting ring 35 mounted to the front frame member 14 anddefining an internal curved anvil surface 36 having a diametercorresponding generally to the diameter of the circle defined by therollers 26-32. Thus the rollers 26-32 and anvil means 34 form andmaintain the sheet material in a transversely arcuate configuration. Thecurved anvil surface 36 will be seen to have a circumferential lengthsomewhat greater than the width of the sheet material 25.

Means for advancing the sheet material through the apparatus, preferablyin a continuous is provided and comprises a pair of flexible, curveddrive rollers 37 and I 38 mounted inside the rear portion of anvilsurface 36 and cooperating with the interior surface thereof to formnips through which the sheet material passes as seen in FIG. 4. Each ofthe rollers comprises a flexible plastic tubular inner member 40 and anouter sheath 41 of relatively soft foam rubber which has a highcoefficient of friction to not only facilitate the advancement of thesheet material but to prevent transverse movement of the sheet materialas it passes the slitting station. The inner member 40 of each rollerextends axially beyond the ends of the sheath 41 and is loosely carriedon a split circular rod 42 such that the rod 42 forms the central coreof each roller.

The rod 42 is retained at its upper portion by the bracket 44 and at itslower portion by the bracket 46, note FIGS. 4 and 9. The brackets 44 and46 are in turn secured to a fixed cylindrical guide ring 48 having anouter surface adapted to'engage the inside surface of the advancingsheet material to guide the same into the nips formed by the anvil ring35 and rollers 37 and 38.

. To rotate the rollers 37 and 38, a pair of sprockets 50, 51 arerotatably positioned on the rod 42 with one sprocket on each side of thelower bracket 46. Each sprocket includes a hub 52, 53 respectively formounting the exposed ends of the inner member 40. A third sprocket 54 isrotatably positioned on the rod 42 adjacent the upper bracket 44 andincludes a pair of oppositely facing hubs 55, 56 each receiving anexposed end of the adjacent inner member 40. The sprockets 50, 51 and 54are rotated by an arrangement which includes a drive motor 58 andsprocket 59, a following sprocket 60 mounted on shaft 61, sprockets 62and 63 mounted on shaft 61 and cooperating with sprockets t) and 51respectively, sprocket 64 on shaft 61 cooperating with sprocket 65 onshaft 66, and sprocket 67 on shaft 66 cooperating with sprocket 54.Conventional chains (not numbered) are connected between the variouspairs of cooperating sprockets. Thus the drive motor 58, which may be ofthe variable speed type, acts to rotate the sprockets 50, SI, and 54,which in turn rotate the plastic inner member 40 and foam rubber sheath41 of each drive roller about the stationary rod 42. The flexibility andresilience of the inner member 40 and sheath 41 permit the same to berotated about the curved rod while substantially maintaining engagementof the sheath with the anvil surface 36.

The means for slitting the advancing sheet material includes a variablespeed drive motor 70 which is rotatably connected to a shaft 72. Theshaft 7 2 extends along and is concentric with the longitudinal centralaxis defined by the rollers 26-32 and ring 35, and is rotatably mountedto the frame by a pair of spaced bearings 74 and 76. The forward end ofthe-shaft 72 mounts a flange 78 which is adapted to adjustably mount aslide 80. As best seen in FIGS..6,-7 and 8, the flange 78 and slide 80are interconnected by an arrangement which includes a pair of dovetailedside walls 81 and 82 carried by the flange 78. The slide 80 includescorrespondingly shaped side edges, and may be moved laterally in eitherdirection in relation to the shaft 72. To lock the slide in apreselected position, a threaded member 84 is carried by the slide andis adapted to engage the flange 78 as seen in FIG. 7. It will be notedthat the upper portion of the flange 78 mounts a threaded member 86 anda number of weights 87 to serve as an adjustable counter-balance for thepurposes to become apparent. The slide 80 further mounts a second shaft90 and a circular knife 92. The axis of the shaft 90 is parallel to theaxis of shaft 72 but will normally be somewhat axially off-set oreccentric in the manner shown in FIG. 3. The knife 92 has a diametersomewhat less than the diameter of the anvil surface 36, and isconnected to the shaft 90 by a bearing 94 such that the knife isessentially free wheeling. The periphery of the knife includes aplurality of spaced interruptions 96 defining a plurality of spacedcutting edges 97. By design, the central axis of the knife (or axis ofshaft 90) is eccentric to the axis defined by the ring 35 and shaft 72by an amount substantially equal to the difference between the radius ofthe knife and that of the anvil surface 36. Thus as the shaft 72 isrotated, the radially outermost portion of the knife 92 walks along orcircumscribes the anvil surface 36 and rotates an increment of arevolution in a direction opposite to the rotation of shaft 72 for eachrevolution of the shaft 72. The rela'tivediameters of the anvil surface36 and knife 92 are so chosen that the increment of a revolution whichthe knife 92 rotates for each revolution of shaft 72 provides thepredetermined staggered relation of the slits in adjacent rows.

ln operation, the sheet material 25 is withdrawn from its supply rolland continuously advanced along a path of travel extending through theapparatus by the drive rollers 37 and 38. The material enters the rearend of the apparatus, is rolled or formed into a transversely curvedconfiguration by the idler rollers 26-32 riding on the exterior surfaceof the material, and is maintained in this configuration by the guidering 48 and also by the drive rollers 37-38 and ring 35.

As the material 25 passes through the ring 35, the radially outermostcutting edges 97 of the circular knife blade 92 will circumscribe thecircumference of the advancing sheet material. Since the outer peripheryof the knife blade substantially engages the anvil surface 36 of thering 35, the cutting edges 97 will penetrate the material 25 and form aplurality of spaced slits along the circumference of the sheet material.The process is repeated as the material is advanced to form paralleltransverse rows of spaced slits when the material is laid flat afterleaving the ring 35. If the material 25 is continuously advanced, thetransverse rows will extend thereacross on a slight bias which will varydepending upon the relative speeds of advancement of the material androtation of knife 92.

It will be apparent that the apparatus is easily adapted to fabricateany desired configuration of slits in the material. In this regard, theknife 92 can easily be replaced by a knife having a somewhat differentedge design or diameter, and the speed of either feed drive motor 58 orslitting motor can be varied to adjust the spacing between thetransverse rows. Preferably however, the blade will be designed so as tobe rotated an increment of a revolution upon each traversal of thecutting surface of the material 25 so that the slits in adjacent rowswill be in a predetermined staggered relation.

In the drawings and specification, there has been set forth a preferredembodiment of the invention, and although specific terms are employed,they are used in a generic and descriptive sense only and not forpurposes of limitation.

I claim: 1. An apparatus for slitting sheet material of indeterminatelength in a predetermined pattern of spaced apart rows of spaced slitswith the slits in adjacent rows being in predetermined staggeredrelation to form a web capable of being expanded into a relatively open,net-like structure, said apparatus comprising means for advancing thesheet material longitudinally along a predetermined path of travel toand past a slitting station,

means operatively associated with said advancing means for forming thesheet material being fed to the slitting station into a transverselycurved configuration and means operatively associated with saidadvancing means for slitting the transversely curved sheet material atthe slitting station to form transversely extending, spaced rows ofspaced slits with the slits in adjacent rows being in predeterminedstaggered relation.

2. An apparatus for slitting sheet material of indeterminate length in apredetermined pattern of spaced apart rows of spaced slits with theslits in adjacent rows being in predetermined staggered relation to forma web capable of being expanded into a relatively open net-likestructure, said apparatus comprising knife means mounted for rotationabout an axis and having a cutting surface for forming closely spacedrows of spaced slits in the sheet material means for advancing the sheetmaterial along a path of travel parallel to said axis of said knifemeans, and

. means for successively traversing the cutting surface of said knifemeans transversely of the sheet material to form successive rows ofspaced slits, the knife means being rotated an increment of a revolutionupon each traversal of the cutting surface of the sheet material so thatthe slits in adjacent rows are in predetermined staggered relation.

3. Apparatus according to claim 2 wherein advancing means comprises feedmeans for feeding the sheet material past said knife means and variabledrive means connected to said feed means for driving said feed means ata variable rate to vary the spacing between adjacent rows of slits.

4. Apparatus according to claim 2 wherein said traversing meanstraverses the cutting surface of said knife means transversely of thesheet material at a variable rate relative to the rate at which thesheet material is advanced to vary the spacing between adjacent rows ofslits.

5. Apparatus according to claim 2 including anvil means cooperating withsaid knife means and said advancing means for supporting the sheetmaterial during slitting thereof.

6. Apparatus according to claim 5 wherein said knife means is generallycircular and the cutting surface thereof includes circumferentiallyspaced cutting edges of predetermined circumferential lengthscorresponding to the desired lengths of the slits to be formed.

7. Apparatus according to claim 6 wherein said anvil means defines acurved anvil surface of larger radius than said knife means, and whereinsaid advancing means cooperates with said anvil means in forming thesheet material into a transversely curved configuration corresponding tothe curve of said anvil surface.

8. An apparatus for slitting sheet material of indeterminate length in apredetermined pattern of spaced apart rows of spaced slits with theslits in adjacent rows being in predetermined staggered relation to forma web capable of being expanded into a relatively open, net-likestructure, said apparatus comprising a circular knife mounted forrotation about a central axis and having a cutting surface defined bycircumferentially spaced cutting edges of predetermined circumferentiallength for forming successive rows of spaced slits in the sheetmaterial, means defining a curved anvil surface surrounding at least aportion of said knife and having a circumferential length at least asgreat as the width of the sheet material and a radius greater than theradius of said knife,

means for advancing the sheet material along a path parallel to saidaxis of said knife and between said curved anvil surface and said knifemeans and cooperating with said .curved anvil surface for forming thesheet material into a transversely curved configuration corresponding tothe curve of said anvil surface, and

means mounting said knife for eccentric rotation about an axisconcentric with said curved anvil surface with the amount that saidcentral axis of said knife is eccentric to said concentric axis beingsubstantially equal to the difference between the radius of said knifemeans and said curved anvil surface so that upon rotation of the knifemeans about said concentric axis the cutting surface of the knife meanswill be traversed along said curved anvil surface and transversely ofthe sheet material to form successive rows of slits therein.

9. Apparatus according to claim 8 wherein said advancing means comprisesat least one curved roll contiguous to said curved anvil surfacerearwardly of said knife but adjacent thereto for advancing the sheetmaterial while maintaining the same against the anvil surface as theknife slits the same.

10. Apparatus according to claim 8 wherein said anvil surface issubstantially right cylindrical.

11. Apparatus according to claim 10 wherein said advancing meanscomprises a pair of circumferentially spaced, curved rolls contiguous tosaid cylindrical anvil surface rearwardly of but adjacent to said knifefor advancing the sheet material while maintaining the same against theanvil surface as the knife slits the same and means connected to saidcurved rolls for driving the same.

12. Apparatus according to claim 8 wherein said mounting means for saidknife includes a first shaft mounted concentric with said curved anvilsurface, a second shaft concentric with said knife and mounting saidknife thereon, and means mounting said second shaft on said first shaftand in eccentric relation thereto.

13. Apparatus according to claim 12 wherein said means mounting saidsecond shaft on said first shaft is adjustable to vary the amount ofeccentricity between the first and second shafts so that knives ofvarying diameter may be used with said anvil surface.

14. A method of slitting sheet material of indeterminate length in apredetermined pattern of spaced apart rows of spaced slits with theslits in adjacent rows being in predetermined staggered relation to forma web capable of being expanded into a relatively open, net-likestructure, said method comprising advancing the sheet materiallongitudinally in a predetermined path of travel to a slitting stationwhile forming the sheet material into a transversely curvedconfiguration, and

slitting the transversely curved sheet material at the the slittingstation to form transversely extending, spaced rows of spaced slits withthe slits in adjacent rows in predetermined staggered relation.

15. A method according to claim 14 wherein the sheet material is formedinto a transversely arcuate configuration and wherein the sheet materialis slit by traversing the sheet material with a rotary knife means.

16. A method according to claim 14 wherein the sheet material isadvanced longitudinally at a variable rate to vary the spacing betweenadjacent rows of slits.

1. An apparatus for slitting sheet material of indeterminate length in apredetermined pattern of spaced apart rows of spaced slits with theslits in adjacent rows being in predetermined staggered relation to forma web capable of being expanded into a relatively open, net-likestructure, said apparatus comprising means for advancing the sheetmaterial longitudinally along a predetermined path of travel to and pasta slitting station, means operatively associated with said advancingmeans for forming the sheet material being fed to the slitting stationinto a transversely curved configuration and means operativelyassociated with said advancing means for slitting the transverselycurved sheet material at the slitting station to form transverselyextending, spaced rows of spaced slits with the slits in adjacent rowsbeing in predetermined staggered relation.
 1. An apparatus for slittingsheet material of indeterminate length in a predetermined pattern ofspaced apart rows of spaced slits with the slits in adjacent rows beingin predetermined staggered relation to form a web capable of beingexpanded into a relatively open, net-like structure, said apparatuscomprising means for advancing the sheet material longitudinally along apredetermined path of travel to and past a slitting station, meansoperatively associated with said advancing means for forming the sheetmaterial being fed to the slitting station into a transversely curvedconfiguration and means operatively associated with said advancing meansfor slitting the transversely curved sheet material at the slittingstation to form transversely extending, spaced rows of spaced slits withthe slits in adjacent rows being in predetermined staggered relation. 2.An apparatus for slitting sheet material of indeterminate length in apredetermined pattern of spaced apart rows of spaced slits with theslits in adjacent rows being in predetermined staggered relation to forma web capable of being expanded into a relatively open net-likestructure, said apparatus comprising knife means mounted for rotationabout an axis and having a cutting surface for forming closely spacedrows of spaced slits in the sheet material means for advancing the sheetmaterial along a path of travel parallel to said axis of said knifemeans, and means for successively traversing the cutting surface of saidknife means transversely of the sheet materIal to form successive rowsof spaced slits, the knife means being rotated an increment of arevolution upon each traversal of the cutting surface of the sheetmaterial so that the slits in adjacent rows are in predeterminedstaggered relation.
 3. Apparatus according to claim 2 wherein advancingmeans comprises feed means for feeding the sheet material past saidknife means and variable drive means connected to said feed means fordriving said feed means at a variable rate to vary the spacing betweenadjacent rows of slits.
 4. Apparatus according to claim 2 wherein saidtraversing means traverses the cutting surface of said knife meanstransversely of the sheet material at a variable rate relative to therate at which the sheet material is advanced to vary the spacing betweenadjacent rows of slits.
 5. Apparatus according to claim 2 includinganvil means cooperating with said knife means and said advancing meansfor supporting the sheet material during slitting thereof.
 6. Apparatusaccording to claim 5 wherein said knife means is generally circular andthe cutting surface thereof includes circumferentially spaced cuttingedges of predetermined circumferential lengths corresponding to thedesired lengths of the slits to be formed.
 7. Apparatus according toclaim 6 wherein said anvil means defines a curved anvil surface oflarger radius than said knife means, and wherein said advancing meanscooperates with said anvil means in forming the sheet material into atransversely curved configuration corresponding to the curve of saidanvil surface.
 8. An apparatus for slitting sheet material ofindeterminate length in a predetermined pattern of spaced apart rows ofspaced slits with the slits in adjacent rows being in predeterminedstaggered relation to form a web capable of being expanded into arelatively open, net-like structure, said apparatus comprising acircular knife mounted for rotation about a central axis and having acutting surface defined by circumferentially spaced cutting edges ofpredetermined circumferential length for forming successive rows ofspaced slits in the sheet material, means defining a curved anvilsurface surrounding at least a portion of said knife and having acircumferential length at least as great as the width of the sheetmaterial and a radius greater than the radius of said knife, means foradvancing the sheet material along a path parallel to said axis of saidknife and between said curved anvil surface and said knife means andcooperating with said curved anvil surface for forming the sheetmaterial into a transversely curved configuration corresponding to thecurve of said anvil surface, and means mounting said knife for eccentricrotation about an axis concentric with said curved anvil surface withthe amount that said central axis of said knife is eccentric to saidconcentric axis being substantially equal to the difference between theradius of said knife means and said curved anvil surface so that uponrotation of the knife means about said concentric axis the cuttingsurface of the knife means will be traversed along said curved anvilsurface and transversely of the sheet material to form successive rowsof slits therein.
 9. Apparatus according to claim 8 wherein saidadvancing means comprises at least one curved roll contiguous to saidcurved anvil surface rearwardly of said knife but adjacent thereto foradvancing the sheet material while maintaining the same against theanvil surface as the knife slits the same.
 10. Apparatus according toclaim 8 wherein said anvil surface is substantially right cylindrical.11. Apparatus according to claim 10 wherein said advancing meanscomprises a pair of circumferentially spaced, curved rolls contiguous tosaid cylindrical anvil surface rearwardly of but adjacent to said knifefor advancing the sheet material while maintaining the same against theanvil surface as the knife slits the same and means connected to saidcurved rolls for driving thE same.
 12. Apparatus according to claim 8wherein said mounting means for said knife includes a first shaftmounted concentric with said curved anvil surface, a second shaftconcentric with said knife and mounting said knife thereon, and meansmounting said second shaft on said first shaft and in eccentric relationthereto.
 13. Apparatus according to claim 12 wherein said means mountingsaid second shaft on said first shaft is adjustable to vary the amountof eccentricity between the first and second shafts so that knives ofvarying diameter may be used with said anvil surface.
 14. A method ofslitting sheet material of indeterminate length in a predeterminedpattern of spaced apart rows of spaced slits with the slits in adjacentrows being in predetermined staggered relation to form a web capable ofbeing expanded into a relatively open, net-like structure, said methodcomprising advancing the sheet material longitudinally in apredetermined path of travel to a slitting station while forming thesheet material into a transversely curved configuration, and slittingthe transversely curved sheet material at the the slitting station toform transversely extending, spaced rows of spaced slits with the slitsin adjacent rows in predetermined staggered relation.
 15. A methodaccording to claim 14 wherein the sheet material is formed into atransversely arcuate configuration and wherein the sheet material isslit by traversing the sheet material with a rotary knife means.